The present invention relates to a vane of a compressor to be used, for example, in a rotary compressor or a vane pump.
FIG. 1 shows an example of a known compressor with a vane. A vane 1 is continuously pressed against a rotor 2 by means of a helical compression coil spring 4, so that a gas in the space formed between the rotor 2 and a cylinder 3 is compressed by change in volume thereof due to the eccentric rotation of the rotor 2. A freon gas is conventionally used as the gas acting as the cooling medium.
The terminal end of the vane and the side surfaces of the vane are continuously in sliding-contact with the rotor and the cylinder, respectively. Thus, the required characteristics of a vane is not only that the vane itself does not wear but also that it does not cause wearing of the mating rotor and cylinder. Conventional vanes are produced from high speed steels equivalent to JIS SKH51 by melting and casting processes. In some cases, the thus produced vanes are surface-treated with oxynitriding. Further, proposals have been made with respect to modification in the composition of the material for a vane, improvement in wear resistance and improvement in self-lubricating ability as disclosed in JP-A-56-47550, JP-A-59-20446, JP-A-61-48556, JP-A-64-35091 and JP-A-2-102392.
A freon of the chlorofluorocarbon (hereinafter referred to as CFC) type is used as the cooling medium in the above described compressors. CFC, however, is decomposed by ultraviolet radiation after its diffusion into the stratosphere where it emits chlorine which destroys the ozone layer. For this reason, it is now planned to totally ban CFC by the year 2000, and development of a cooling medium is in progress to replace this. A freon of the hydrofluorocarbon (hereinafter referred to as HFC) type which does not contain chlorine seems to be most promising as the substitute cooling medium. This type of freon is less harmful to the environment.
However, when compared to those using a conventional CFC type freon, a vane pump or rotary compressor using a HFC type freon has the following disadvantages.
(1) Lubricating ability of the cooling medium is inferior. PA1 (2) A higher compression ratio is required, whereby the load to be applied to vane becomes higher. PA1 (3) Hygroscopicity of the cooling medium is high. PA1 (4) Lubricating ability of the lubricant oil is inferior. PA1 (5) Hygroscopicity of the lubricant oil becomes higher.
For the reasons as described above, in the case where a conventional vane is used, the wear resulting from sliding-contact with the rotor is greatly accelerated and, in extreme cases, scatting may be caused with the sliding-contact. It is thus increasingly apparent that lifetime as a practical compressor cannot be obtained.